With the wide application of smart terminals (Smart Phone) and Machine Type Communications (Machine Type Communications, MTC for short) devices, transmission of small data packets becomes increasingly frequent. For example, for a service such as email push (Email Push), instant messaging software MSN or QQ, and a virtual private network (Virtual Private Network, VPN for short) supported by a smart phone, within a period of time during which no service data takes place, to maintain a connection with a server, a keepalive (keep alive) message needs to be exchanged with the server, where the message is a small data packet; for another example, for a service such as smart meter reading, smart traffic, and smart medical care in a Machine to Machine (Machine to Machine, M2M for short) service supported by an MTC device, data transmitted in the service is also a small data packet. In a Universal Mobile Telecommunications System (Universal Mobile Telecommunication System, UMTS for short), user equipment (User Equipment, UE for short) that performs such a service is usually set to an idle mode, and once the UE has a small data packet that needs to be sent, a Radio Resource Control (Radio Resource Control, RRC for short) connection is then set up to send the small data packet.
However, an existing procedure of transmitting a small data packet is lengthy, resulting in a delay in data transmission and relatively low transmission efficiency.